Navigation

Note that it is important to know what elevation
corresponds to for each
topography dataset you might use (i.e. the
vertical datum)
Global ETOPO1 bathymetry is relative to MSL (Mean Sea Level),
while tsunami inundation relief is often relative to MHW (Mean High Water).
These can often be combined since the difference is small relative to the
resolution of the global bathymetry and the result assumed to be relative to
MHW. This is important if comparing to tide gauge observation or when
modeling inundation.

An earthquake source is typically specified by giving the slip along the
fault on a set of fault planes or on subfaults making up a single plane.
This data must then be converted into seafloor deformation to create the
dtopo file needed for GeoClaw (see Topography displacement files). This conversion
is often done using the Okada model as described at
Earthquake sources: Fault slip and the Okada model.

Tide gauge data is often recorded relative to MLLW (Mean Lower-Low Water), so be
sure to check the
vertical datum.

For example, if you go to a station page such as
Hilo Bay,
you will see a Datums link on the left menu that gives the difference
between MLLW and other water levels such as MHW, which might be the
reference level for the bathymetry. (Be sure to switch from feet to
meters!) Sometimes you can also select the Datum to use when retrieving
data.